As a fuel cell, there is conventionally known a solid oxide type fuel cell (hereinafter sometimes abbreviated as “SOFC”) using a solid electrolyte (solid oxide).
One known use of SOFC is as a fuel cell stack having stacked therein a plurality of single cell elements, each including a plate-shaped solid electrolyte, a fuel electrode disposed on one side of the solid electrolyte and an air electrode disposed on the other side of the solid electrolyte.
The SOFC is so configured as to generate electrical power by supplying fuel gas and air to the fuel electrode and the air electrode, respectively, and causing chemical reaction of the fuel and oxygen in the air through the solid electrolyte.
In some cases, a plate-shaped separator made of metal such as stainless steel (called “metal separator”) is used in the SOFC so as to separate a flow path of fuel gas (i.e. fuel flow path) and a flow path of air (i.e. air flow path) from each other. It has been known to use separator-bonded single cell units in which, when viewed in plan, rectangular frame-shaped metal separators are integrally bonded by brazing around peripheries of rectangular single cell elements.
Further, Patent Document 1 discloses a technique of bonding a surface-aluminized metal member to a ceramic member with the use of a brazing material having a mixed composition of a metal oxide such as Ag—CuO, Ag—V2O5 or Pt—Nb2O5 and a noble metal as a seal material.
Patent Document 2 discloses a technique of brazing a metal member to a ceramic member with the use of a Ti-doped Ag brazing material.